Scabbler bits comprise a plurality of cutting tips, usually of tungsten carbide, fitted in the base of a carrier which in turn is fixed to a reciprocating piston of a scabbling machine. In the conventional form of scabbler bit, the carrier is a female member of closed cylindrical form which fits over a male piston and is secured thereon by a through pin. Our European Pat. No. 0.068,829 illustrates such prior art in greater detail and discusses its disadvantages and the disclosure of said European Patent is incorporated herein by reference.
EP-0,068,829 relates to an improved scabbling bit in which the carrier is a male member retained within a cylindrical recess in the piston. This provides a significant improvement upon earlier scabbling bits, but it has been found that in some circumstances problems can occur. FIG. 1 shows one embodiment of scabbling bit in accordance with EP-0,068,829, in which the carrier 10 has a separate fixing shank 12 which passes through a central aperture 14 of the carrier 10 to be seated in a central bore 16 of the piston 18, in which it is retained by a pin 20. It will be seen that the scabbler tips 22 are substantially aligned with the external diameter of the piston 18. This arrangement is satisfactory when the load on the scabbler bit is substantially axial. However, uneven loading on the scabbler tips, or sideways load, can result in distortion or fracture.
It is accordingly an object of the present invention to provide a scabbler bit of male formation in which the foregoing problems are overcome or mitigated.